Heat Pumps Architecture Optimization For Enhanced Medium Temperature Geothermal Heat Use in District Heating

International audienceUse of geothermal heat in district networks allows increasing the share of renewable energy in the production mix. However, in many cases, this share is limited by the district heating required temperature and seasonal load variation. Heat pumps permit upgrading geothermal heat by further increasing the temperature while pumping residual heat from the network’s return. Therefore not only they substitute boilers for upgrading the temperature but also increase the used share of the geothermal heat source by reducing the return temperature. This paper presents a methodology for heat pumps architecture optimization enhancing the use of geothermal heat. The methodology allows, by considering the total consumed exergy as an objective to minimize, the increase of renewable energy share while considering the best heat pump integration. Many configuration options are considered for the disposal of heat pumps. A case study is presented optimizing the use of a 60°C geothermal source connected to a district in the north of France. The geothermal well has two constraints: a limited mass flowrate and a minimal reinjection temperature of 25°C